brachial vein vs vena

brachial vein and vena both are nouns.

Word	Noun	Adjective	Verb	Adverb
brachial vein	Yes	No	No	No
vena	Yes	No	No	No

As nouns, vena is a hypernym of brachial vein; that is, vena is a word with a broader meaning than brachial vein:

brachial vein: two veins in either arm that accompany the brachial artery and empty into the axillary vein
vena: a blood vessel that carries blood from the capillaries toward the heart

Other hypernyms of brachial vein include vein, venous blood vessel.

brachial vein (noun)	vena (noun)
two veins in either arm that accompany the brachial artery and empty into the axillary vein	a blood vessel that carries blood from the capillaries toward the heart